Date: Tue, 06 May 2014 16:15:46 -0600 From: Ian Lepore <ian@FreeBSD.org> To: John Baldwin <jhb@FreeBSD.org> Cc: Kevin Oberman <rkoberman@gmail.com>, "freebsd-acpi@freebsd.org" <freebsd-acpi@FreeBSD.org>, "freebsd-arch@freebsd.org" <freebsd-arch@FreeBSD.org> Subject: Re: proposal: set default lid state to S3, performance/economy Cx states to Cmax Message-ID: <1399414546.22079.286.camel@revolution.hippie.lan> In-Reply-To: <201405061637.30037.jhb@freebsd.org> References: <CAJ-Vmo=mUtpjgVwNHg8af05vCxVchZdsaekR9_Wf-pOfFjnABQ@mail.gmail.com> <201405051657.49992.jhb@freebsd.org> <CAJ-VmonB=2WV0Zq3SVvuxqqfi%2B=CTEy35DeF01UUzUCoNk5HWg@mail.gmail.com> <201405061637.30037.jhb@freebsd.org>
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On Tue, 2014-05-06 at 16:37 -0400, John Baldwin wrote: > On Tuesday, May 06, 2014 2:08:35 pm Adrian Chadd wrote: > > On 5 May 2014 13:57, John Baldwin <jhb@freebsd.org> wrote: > > > > > The user in question found this on 9-stable with the existing defaults as the > > > HPET was just plain broken on their system and that was unrelated to Cx states. > > > (Rather, Cx states were only involved because worries about them are why the > > > system chose to use HPET. Had Cx states been enabled by default, they would > > > have had to disable those as well in addition to forcing LAPIC instead of > > > HPET.) > > > > Hm. Sounds uncomfortable. How does Windows run on systems like this? > > Do the windows drivers just disable HPET and use LAPIC or worse for > > timing, and just ignore anything lower than C1? > > I have no idea. Maybe they use the RTC. :-/ Maybe the HPET on these systems > works if you use it "sparingly". I believe OS X might have only used the HPET > to provide the "missing" LAPIC wakeups when entering Cx for example. (Our current > eventtimer system wants to always use whichever timer it picks, not switch off > between them.) > The eventtimer code is happy to switch between timers on the fly, but iirc the only interface to that feature is sysctl. I found it fairly easy to add an in-kernel API for changing the frequency of the current timer on the fly. I think it would be just as easy to add a kernel call to change timers as well. -- Ian
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